The invention relates to a double casing for food products, comprised of a flexible tube of an edible or inedible material, shirred, that is externally coated with a length equivalent to the amount of the tube of a tubular net, elastic, semi-elastic or non-elastic disposed coaxially to the tube and compressed or shirred in the same extent as the tube is shirred, so that it occupies an equivalent length.
The beginning of the compressed or shirred tubular net is slightly displaced from the beginning of the shirred tube, so that a few centimeters of the latter are not coated. Between the shirred tube and the compressed tubular net can be provided a cylindrical separation sheet made of any material, such as a plastic film.
The above described assembly can be internally supported by a hollow cylinder made of a stiff material.
The above system, continuously or discontinuously and by way of a simultaneous unshirring of the film and the net, can provide a double wrapping formed by the overlapping film and the tubular net that that can be filled by closing the film and the net jointly on the open end and stuffing inside a solid or semisolid product with a stuffing horn placed inside the support tube of the assembly.
The area of shirred film not coated by the compressed or shirred tubular net ensures that the latter will not prevent the shirred film from unfolding easily because of the compression force exerted on it. As the film and the net are unshirred to form the casing, the front ends of the shirred film and net move back in the same extent, so that there is always an area of uncoated and free shirred film. The separation sheet allows the film to become unshirred uniformly and ensures that the portion of shirred film that is not coated by the compressed net is not carried away by the latter as it unfolds.
The product described can be used for manual or automatic packaging of food products that may or may not be later subjected to any processes of drying, maturing, curing, cooking, sterilization, etc., in which the film casing and outer net assembly are required.
The invention also relates to the method for manufacturing said product.
The use of double casings for meat products, and specifically those externally including string, mesh or nets has been traditionally employed for several purposes, among which are the following:
1)As a decorative mechanism in order to give the product an external appearance with a greater finish in some cases, or more traditional and artisan-like in others. In other cases, the object is to ensure that the finished product maintains the characteristic mark made by the net after the casing is removed.
2)As an additional compression system for the first casing, so that air is eliminated more effectively to obtain an improved appearance and conservation of the products, or to hold tightly the stuffed product during the cooking process in order to achieve a proper bonding of the meat. For products undergoing a drying process, the mesh, string or net help the tripe remain joined to the surface of the product despite the shrinkage resulting from the drying process.
3)As a system for holding the inner casing so that the entire stuffed piece maintains a uniform gauge. This is important for casings made of plastic, collagen or regenerated cellulose of large caliber with a tendency for their diameter to vary. Coating these pieces with semi-elastic or non-elastic nets helps solve this problem.
4)As a system for hanging the products, whether for their heat treatment in cooking ovens or for a drying process. The external coating of string, mesh or net provides, in addition to a basic hanging system, an effective support for the weight of the product which in many cases keeps the casing from breaking.
Traditionally, this second external casing is placed manually as an additional operation after the first casing is stuffed. This operation has always been labor-intensive.
One of the first improvements of the traditional method is described in U.S. Pat. No. 1,505,218 (Sartore, 1924) and consists of a double casing comprising an inner cylindrical tube coated by a cylindrical net. This double casing is cut into segments of a length matching that of a piece of the final product to be stuffed. The advantages provided over the traditional method is to give the internal piece a greater resistance, so that it can be stuffed at a higher pressure, thereby eliminating the air more efficiently and reducing the number of breakages, but above all, reducing the time required to place the net after stuffing with the ensuing savings in labor costs.
A second improvement is described in U.S. Pat. No. 5,024,041 (Urban, 1991), which describes a method where both the inner casing and the outer net are shirred, the former on the stuffing tube of a stuffing machine and the latter on a tube concentric to the aforementioned one having a large enough inner diameter, so that with the two closed by a staple or clip it is possible to perform the stuffing continuously and automatically. This invention also incorporates a retainer brake for the first casing. In addition to these advantages the system also allows a faster stuffing operation.
U.S. Pat. No. 5,980,374 (Mercuri, 1999) provides an additional improvement, and consists of a double casing comprising an inner tubular casing and an outer elastic cylindrical net placed concentrically to each other and later shirred jointly. The advantage is that both components form a single piece and can be used as a traditional simple casing, placing them on the stuffing horn without requiring additional tubes to place the net, and further preventing the need to load said net.
Although all of the aforementioned inventions constitute important improvements of the system, there remain a few significant aspects to resolve. The system disclosed by U.S. Pat. No. 5,024,041 (Urban, 1991), although providing a continuous stuffing method, requires an additional tube to support the net and a system for attaching said tube to the stuffing machine. Additionally, the net must be loaded on this tube in a separate operation, with the corresponding additional time and labor costs. Furthermore, each time the inner casing or net is finished, which are not always simultaneous, it is necessary to stop the operation to replace the exhausted supply. This also slows down the system and increases labor costs.
The system described in U.S. Pat. No. 5,980,374 (Mercuri, 1999), although solving some of the aforementioned problems, such as the need for accessories to support the net, and somewhat reducing the number of stoppages for placing either the inner casing or the net, as their length is substantially the same in each unit of double shirred casing, this approach has a disadvantage in that said length is limited because of the joint shirring of the two components. Thus, in the shirred stick, the length of double casing contained in each fold is at most the distance between the elastic transversal threads of the net, as during the shirring operation and as described in the corresponding patent, the elastic transversal threads are placed spontaneously at the troughs of the folds, thereby limiting the length of the double casing contained in each one. In addition, the number of folds per unit length contained in the stick depends on the thickness of each fold, that is, the sum of the thickness of the inner casing and the thickness of the elastic thread.